So very much has changed (not only in "food" itself but within things that affect the world of "food") since the times of our grand-parents and great-grandparents, particularly if we fit within that group called "baby-boomers".
I'm sure Pollan simplified his thoughts into phrases that would sit on the tongue well for repetition. In order to have concepts remembered by masses of people they have to sing well. He writes extremely well in that way, for his phrases do get remembered and repeated. (That is one thing that sets him aside from many writers springing from an academic background - he can take off the wordy clutter and dance.)
There was not only "opportunity for ersatz" in the past as Ilaine wrote above, but there was "actual" ersatz food.
There has been ersatz food around at least since Ancient Rome.
And the ersatz food often gets consumed by those who can not afford that which is not ersatz, for ersatz often is less expensive (in terms of initial cost, of course)(but the poor mostly think of initial cost, as they must - having no excess finances to spare).
Pollan has stayed away from some topics, as well he should. Otherwise his manifestos, so easily taken up and embraced, would become cumbersome and potentially too difficult and/or time-consuming for the general reader to wade through in a mass market book.
The topics of class, racial/ethnic interaction and attitudes in the US, changes in urban and rural living, the fact that no longer is it presumed that there is a woman or servant in the kitchen from the AM to the PM, the new science of marketing that Madison Avenue wields with its right arm the information superhighway - all these topics have weight within the putting-things-to-work and the how-things-did-work of Pollan's questions and will have weight, finally, in how his answers can or will play out, today and in the future.
Ersatz is what you make it. Ersatz has been made interesting. Ersatz has been made both cheaper and more expensive. Ersatz, though, often - is taken up by the group of the public that can not afford better. Whether they are interested - or not.
And of course some are interested. Always have been. For ersatz is a taste. A simpler and less complex taste. A cheap and shiny taste? A to-hell-with-it-all-it's-all-about-me-right-now-taste?
Sometimes I am reminded that vulgar is a Latin term.
There's a song running through my head right now - a country song. "I Like My Women a Little on the Trashy Side". Goes for food, too - some times, some places, some people.
Goodness knows I eat a Twinkie now and then.
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Anna, you know I have several stories about what my mother (who would be some people's grandmother's age) and my grandmother "recognized as food". In my opinion, in my house - we've come a long way.

That fact in no way takes away from what Michael Pollan has provided us all in terms of food for thought and hopefully concepts to use, whether his phrases and questions have been simplified for easy use or not.